group array in javascript code example

Example 1: javascript array group by

function groupByKey(array, key) {
   return array
     .reduce((hash, obj) => {
       if(obj[key] === undefined) return hash; 
       return Object.assign(hash, { [obj[key]]:( hash[obj[key]] || [] ).concat(obj)})
     }, {})
}


var cars = [{'make':'audi','model':'r8','year':'2012'},{'make':'audi','model':'rs5','year':'2013'},{'make':'ford','model':'mustang','year':'2012'},{'make':'ford','model':'fusion','year':'2015'},{'make':'kia','model':'optima','year':'2012'}];

var result = groupByKey(cars, 'make');

JSON.stringify(result,"","\t");
{
	"audi": [
		{
			"make": "audi",
			"model": "r8",
			"year": "2012"
		},
		{
			"make": "audi",
			"model": "rs5",
			"year": "2013"
		}
	],
	"ford": [
		{
			"make": "ford",
			"model": "mustang",
			"year": "2012"
		},
		{
			"make": "ford",
			"model": "fusion",
			"year": "2015"
		}
	],
	"kia": [
		{
			"make": "kia",
			"model": "optima",
			"year": "2012"
		}
	]
}

Example 2: group objects in javascript

function groupBy(arr, prop) {
    const map = new Map(Array.from(arr, obj => [obj[prop], []]));
    arr.forEach(obj => map.get(obj[prop]).push(obj));
    return Array.from(map.values());
}

const data = [{ name: "Display", group: "Technical detals", id: 60, value: 4 }, { name: "Manufacturer", group: "Manufacturer", id: 58, value: "Apple" }, { name: "OS", group: "Technical detals", id: 37, value: "Apple iOS" }];
	
console.log(groupBy(data, "group"));

Example 3: javascript array group by id

var results = orgs.reduce(function(results, org) {
    (results[org.id] = results[org.id] || []).push(org);
    return results;
}, {})